1. Field of the Invention
The present invention concerns a method enabling a mobile station of a cellular mobile radio system with more than one type of cell to determine the type of cell it is accessing. The invention also concerns a mobile station and a base transceiver station for implementing this method.
2. Description of the Prior Art
A cellular mobile radio system is either a simple system such as the GSM system, the DECT system, the DCS 1800 system, etc or a more complex system combining a plurality of simple systems.
In some simple cellular mobile radio systems currently at the design stage there is provision for using more than one type of cell. Each type of cell can be characterized by its own bit rate, its own modulation, its own coding, its own data packet (or burst) structure, its own baseband signal processing, etc. This applies in particular to so-called third generation systems (future mobile radio systems).
The use of different types of cells enables adaptation of the air interface between the mobile stations and the system management network to suit the location and the environment of each cell. For example, some modulation methods are more suitable than others if a mobile station is inside the building, lower bit rates are preferable in large diameter cells, and so on.
Accordingly, it is essential for a mobile station accessing a given cell, i.e. within range of the base transceiver station of the cell and able to exchange with the latter signals comprising signalling data or user data, speech or other data, to be able to determine as quickly and simply as possible which type of cell this is, in order to know its characteristics and thus to be able to exchange signals effectively.
Present day mobile radio systems include only one type of cell. The problem of determining the cell type therefore does not arise in these systems.
Evidently this facility to determine the cell type will be essential in future mobile radio systems with more than one type of cell.
Also under consideration at present is the development of mobile stations able to access different simple cellular mobile radio systems constituting a complex system, these various systems usually each using cells with different characteristics so that the complex system is one with more than one type of cell.
Mobile stations accessing such systems must also be able to determine the type of cell in which they are located.
An object of the present invention is to provide a method enabling a mobile station to determine simply and quickly the type of cell in which it is located.